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# Sparse reordering functions

This module contains all sparse reordering routines.

## hipsparseXcsrcolor()

hipsparseStatus_t hipsparseScsrcolor(hipsparseHandle_t handle, int m, int nnz, const hipsparseMatDescr_t descrA, const float *csrValA, const int *csrRowPtrA, const int *csrColIndA, const float *fractionToColor, int *ncolors, int *coloring, int *reordering, hipsparseColorInfo_t info)

hipsparseStatus_t hipsparseDcsrcolor(hipsparseHandle_t handle, int m, int nnz, const hipsparseMatDescr_t descrA, const double *csrValA, const int *csrRowPtrA, const int *csrColIndA, const double *fractionToColor, int *ncolors, int *coloring, int *reordering, hipsparseColorInfo_t info)

hipsparseStatus_t hipsparseCcsrcolor(hipsparseHandle_t handle, int m, int nnz, const hipsparseMatDescr_t descrA, const hipComplex *csrValA, const int *csrRowPtrA, const int *csrColIndA, const float *fractionToColor, int *ncolors, int *coloring, int *reordering, hipsparseColorInfo_t info)

hipsparseStatus_t hipsparseZcsrcolor(hipsparseHandle_t handle, int m, int nnz, const hipsparseMatDescr_t descrA, const hipDoubleComplex *csrValA, const int *csrRowPtrA, const int *csrColIndA, const double *fractionToColor, int *ncolors, int *coloring, int *reordering, hipsparseColorInfo_t info)

  Coloring of the adjacency graph of the matrix \(A\) stored in the CSR format.

  `hipsparseXcsrcolor` performs the coloring of the undirected graph represented by the (symmetric) sparsity pattern of the matrix \(A\) stored in CSR format. Graph coloring is a way of coloring the nodes of a graph such that no two adjacent nodes are of the same color. The `fractionToColor` is a parameter to only color a given percentage of the graph nodes, the remaining uncolored nodes receive distinct new colors. The optional `reordering` array is a permutation array such that unknowns of the same color are grouped. The matrix \(A\) must be stored as a general matrix with a symmetric sparsity pattern, and if the matrix \(A\) is non-symmetric then the user is responsible to provide the symmetric part \(\frac{A+A^T}{2}\).

  Parameters:

    - handle – [in] handle to the hipsparse library context queue.

    - m – [in] number of rows of sparse matrix \(A\).

    - nnz – [in] number of non-zero entries of sparse matrix \(A\).

    - descrA – [in] sparse matrix descriptor.

    - csrValA – [in] array of `nnz` elements of the sparse CSR matrix.

    - csrRowPtrA – [in] array of `m+1` elements that point to the start of every row of the sparse CSR matrix.

    - csrColIndA – [in] array of `nnz` elements containing the column indices of the sparse CSR matrix.

    - fractionToColor – [in] fraction of nodes to be colored, which should be in the interval \([0.0,1.0]\), for example \(0.8\) implies that \(80\) percent of nodes will be colored.

    - ncolors – [out] resulting number of distinct colors.

    - coloring – [out] resulting mapping of colors.

    - reordering – [out] optional resulting reordering permutation if `reordering` is a non-null pointer.

    - info – [inout] structure that holds the information collected during the coloring algorithm.

  Return values:

    - HIPSPARSE_STATUS_SUCCESS – the operation completed successfully.

    - HIPSPARSE_STATUS_INVALID_VALUE – `handle`, `m`, `nnz`, `descrA`, `csrValA`, `csrRowPtrA`, `csrColIndA`, `fractionToColor`, `ncolors`, `coloring` or `info` pointer is invalid.